In a large bowl, combine the flour, baking powder and salt. In a mixing bowl, cream butter and sugar. Add eggs, milk and vanilla; mix well. Stir in dry ingredients just until moistened. Fold in frozen blueberries.
Fill greased or paper-lined muffin cups two-thirds full. Combine sugar and nutmeg; sprinkle over muffins. Bake at 375 degrees F or 190 degrees C for 20-25 minutes or until muffins test done. Cool in pan for 10 minutes before removing to a wire rack.
Frost is a common problem with wild blueberries and is the primary cause of a poor harvest. Not all blueberry farms have the same climate. The fields in Quebec and Maine blossom before the fields on Prince Edward Island and are therefore more susceptible to frost. The later blossoming of Island berries usually occurs after the last frost of the spring.